Retractable guards for air intakes



y 1 ,1950 1'. H. KERRY ETAL 2,944,631

I I RETRACTABLE GUARDS FOR AIR INTAKES Filed-mamas, 195s Z-Sheets-Sheet1 4 i l ri gv Inventors Attorney! July 12, 1960 'r. H. KERRY L 2,944,631

RETRACTABLE GUARDS FOR AIR INTAKES Fi led Dec. 26, 1956 2 Sheets-Sheet 2FIG.'4.

Inventors) y M M- Attorneys United es Patent Office 2,944,631 PatentedJuly 12,1960

, 2,944,631 RETRACTABLE GUARDS ro AIR INTAKES Thomas Henry Kerry,

Littleover, England, assignors to Rolls-Royce Limited, 7. Derby,England, a British company Filed Dec. 26,1956, Ser, No. 630,643 I Claimspriority, application Great Britain Jan. 6,1956

3"Claims. (Cl. 183-62) This invention relates" to retractable guards forair intakes such as are used, for example, in conjunctionwithgas-turbine power plants. g It has preyiou'sl been proposed to providein an annular air intake a'debris guard arrangement comprising a numberof 'gridvp'ortions' each formed substantially as a sector of the annulusand arranged to swing about circumferentially-extending axes adjacentthe outer edges of the respective grid portions between an operativeposition in which the grid portions together extend across the whole ofthe path of a fluid flowing in the air intake,

Derby, and Peter Arthur Ward,

The guard'portions may be in the'form of grids composed of a number ofbars, the spacing of which will be such as to catch debris entrained inthe fluid, and the bars may be in the form ofstrips which are fiat inone plane and are arranged in two sets, those of one set lying in planesparallel to the axis of the intake duct and extending substantiallylengthwise of the duct when the guard portion is in its inoperativeposition, and-those of the otherset being curved and lying in planeswhich are at right-angles to the abovementioned-planes and are parallelto the axis of the duct when the guard grid is in its operativeposition.

thereby to catch debris entrained in the 'fluid, and an inoperativeposition in which the grid'portions lie out of the path of the fluid andare accommodated within an outer wall of the annular air intake duct.

The present. inventionis applicable to air intake ducts which are ofnon-annular form, for example, 'of full 'cir- 3 cular form or ofrectangular form, and has for anobject to provide an improvedconstruction of retractable guard arrangement.

According to the present invention a retractable guard comprises twoguard portions each of which is mounted to pivot, about an axisextending across the duct, between an operative position in which theguard portions together extend, across the whole of the path of fluidflowing in the duct, one edge of each guard portion cooperates with acorresponding edge of the other guard portion and another edge of eachguard portion co-operates with a wall of the duct, and an inoperativeposition in which the guard portions are substantially out of the pathof fluid flowing through the duct, the guard portions being so shaped asto conform with the wall of the duct against a a which they lie in theretracted position.

Where the intake duct is of full circular form the two guard portionsmay be pivoted about a diameter of the duct, and in this case each guardportion will be of part-cylindrical form, where the duct is of constantdiameter in the length swept by the guard portions, or of partconicalform, where'the duct is varying, for example, of gradually increasingdiameter in that length, so'thatthe guard portions conform with thecorrespondingly-shaped wall of the duct; i I

By a guard of full circular-form is meant one in which the cross sectionof the intake where the guard is fitted is circular.

According to a feature of the invention, the retractable guard comprisesa pair of guard portions which are mounted to pivot about a common axisextending centrally across the duct, and the guard portions meet when in,-In an'alternative arrangement the guard portions may be 'imperforate,being provided: in this case to prevent a flow of air through the enginewhen the latter is shut down, and thus to prevent windmilling of theengine.

In yet another arrangement there may be provided two guard portions inaccordance with the invention formed as grids, and there may be providedin addition two imperforate panels which substantially conform to theshape of the grid portions and which are arranged to move from aninoperative position, in which they are out of the path of the fluid, toan operative position in which they lie against the guard grid portionswhen these are in their operative position. I

,One' embodiment of this invention will now be described with referenceto the accompanying drawings of which 7 Figure Us 'a perspective viewshowing the guard grid in the operative position, v

Figure 2 is a view corresponding to Figure lwith the guard grid in theinoperative position, and

I Figure 3 is a longitudinal section. Figure 4 is a view lookingdownwardly in Figure 3 with the top half of the nacelle removed. 1 1Referring; to Figure ,l the guard grid arrangement is shown as appliedto an air'intake for a gas-turbine engine in a nacelle.

The nacelle 10 has inner and outer walls 11, 12, the inner wall formingthe boundary of a fully circular crosssection air intake, duct 1'3 andthe outer wall 12 forming Ward end which faces in the direction offlight of the aircraft of which the nacelle is to form part and leads atits rear end to the air entry of an axial-flow compressor 16 ofages-turbine engine. 1

As is well known, it is desirable to prevent birds'a'nd otherforeign'bodies from passing down the air intake entrained in theentering air andstri-kin'g the inlet vanes or blades of the compressor16, and for thispurpose there is provided a guard grid arrangement whichwill now be described. V I

The guard grid arrangement comprises a pair of guard grid portions 17,each of which comprises a number of bars arranged in two sets 18, 19.Each bar is of a'flat, substantially rectangular cross-section, of whichthe length issay 12 times \the width, and the ends of the cross-sectioni.e. the edges of the bars may be rounded. The

bars 18 of one set lie in parallel planes and extend,'when-- theguard-grid portions are in theinoperative position, as

shown in Figure 2; parallel to the axis 20 of the air intake 13. Thebars 19 of-the other setextend in planes which are at right angles'tothe-planes in which the =bars 18 of the first set lie, the bars of thetwo sets thus being in planes at right-angles to one another, and bothset's of planes when the guard grid portions are in their operativepositions (as seen in Figure 1), being parallel tothe axis 20 of theintake. Forexample, as shown in Figure 1, the

bars of the first set 18 may lie in parallel vertical planes and thebars 19 of the second set in parallel horizontal planes. The bars 19 ofthe second set are curved in the planes in which they lie, and areinterconnected with the bars 18 of the first set; for example, each barof one set may be formed with a slot which extends half-way through itscross-section and the bars of the other set may be formed with aco-operating slot, the bars interengaging so that the remainder of thecross-section of one bar lies in the slot in the other bar.

The edges of the guard grid portions 17 are formed of parts 21, 22 ofincreased cross-section area for strengthening purposes, one 21 of theseparts lying parallel to the bars'19 of the second set, and the other 22being at an angle which is somewhat less than a right angle to the bars18 of the first set.

Thus each of the guard grid portions 17 has the form of part of thesurface of a cylinder, and accordingly when they are in the inoperativeposition as shown in Figure 2 they substantially conform with thecylindrical inner wall 11 of the nacelle.

There may be provided a recess 23 in the wall 11 of the nacelle, whichextends over that part of the wall adjacent to which the guard gridportions 17 lie when in the inoperative position, for the purpose ofreceiving debris accumulated by the grid portions. It has been foundthat owing to the force of the impact of the debris on the gripportions, the debris tends to be retained on these portions. It may,however, be arranged that the frame 21' of each guard grid portion '17co-operates closely with the edge 24 of the recess 23 in the inner wall11 when the guard grid portions are in the inoperative position, inorder to prevent such debris from becoming loose during flight andentering the air intake of the compressor 16.

The guard grid portions 17 are mounted, as shown, to pivot about an axis25 which is a diameter of the circular-section air intake duct 13, andthis diameter may conveniently be horizontal. Each guard could beindividually mounted to pivot on an axis which is a chord of the duct,the two axes being parallel or even coincident. Each guard grid portion17 will be provided with a pair of sockets 26 at the intersections ofthe two frame members 21, 22, the sockets 26 of one guard grid portion17 lying within those of the other portion with respect to the intakeduct, and engaging with t-runnions 27 which may be spigot memberscarried by the nacelle wall 11.

Suitable operating mechanism will be provided for the guard gridportions 17, and this may comprise a ram, which may be, for example,pneumatically or hydraulically operated, and comprises a cylinder 28, ofwhich one end is secured to the nacelle wall structure, and a pistonwhich is connected by the rod 2% to a lever arm 30 attached to the framemember 22 of the guard grid portion 17. A separate ram may be providedfor each grid portion, in which case stops will be provided to ensurethat each grid portion moves to its appropriate positions, shown inFigures 1 and 2, or alternatively, as shown in the figures, a single rammay be provided and the guard grid portions 17 may be interlinked bymeans of pairs of links 31, one end of the links of each pair beingconnected one to each of the frame members 22 of the grid portions andthe other end of the links being interconnected and carrying a roller 32which co-operates with a corresponding track 33 afforded by the innerwall 11 of the nacelle structure. In this way symmetry of movement ofthe grid portions may be ensured during opening and closing. It will bearranged that the frame member 22 of each grid portion co-operates witha part-spherical surface 34 onthe wall 11 of the intake duct, the framemember 22 moving over the part-spherical surface 34 during movement ofthe guard grid portion 17 from the operative to the inoperativeposition. This sealing arrangement ensures that debris is not carriedaround the guard grid portions into the air intake of the compressor.

In addition to the guard grid portions 17 there may be provided a pairof imperforate panels 35 (see Figures 3 and 4) one of which co-operateswith and lies radially outside each of the guard grid portions when thelatter are in their inoperative position. (In the full line position ofthe panels 35 in Figure 3.) The rear part 36 of each of these panels 35is of part-spherical form and lies immediately outside thepart-spherical portion 34 of the inner wall 11 of the nacelle, and eachpanel is preferably of dished form to afford the recess 23above-mentioned in which debris is trapped when the guard grid portions17 are moved to their inoperative position. The imperforate panels 35are also formed with socket members to engage the trunnions 27 carriedby the nacelle inner wall 11 and are thus mounted to pivot about thehorizontal diameter of the intake duct. It may be arranged that theimperforate panels 35 are held in their inoperative position by a latchmechanism 37 which engages their forward edges, and it may be arrangedthat the aerodynamic forces on the panels 35 are such that when thelatches 37 are released the panelsmove into their operative position inwhich they lie over theguard grid portions and abut one another on ahorizontal plane I through the intake. (In the dotted line position ofthe panels 35 in Figure 3.)

In moving to the operative position the part-spherical rear part 36 ofeach imperforate panel 35 travels over and is in sealing engagement withthe external surface of the part-spherical portion 34 of the inner wall11, and

thus no gap occurs between the outer edge of the imperforate panels 35and the stationary wall structure 11 when the panels move to theoperative position.

Means similar to links 31 and track and roller 32, 33 may be providedattached to and outside the panels 35, if desired, to ensuresimultaneous operation. 7

it will be appreciated that the panels 35 may be moved to the operativeposition simultaneously with, or later than the grid portions 17.

In a further modification, instead of the guard portions being formed asgrids to catch debris entrained in air passing into the engine, theguard portions may be made imperfor-ate so that when they are in theoperative position, flow of air into the air intake of the engine isprevented. It will be appreciated that under certain circumstances, :forexample, when damage has been caused to an engine, it is desirable toprevent rotation of the engine due to windmilling and this may beeffected by preventing the flow of air through the engine.

We claim:

1. A two section, retractable guard for the full crosssection of anon-annular air intake duct of an aircraft gas turbine having acontinuous substantially cylindrical wall, said guard sections beingcomplementary when mated to extend across the whole path of fluidflowing in the duct and shaped to conform throughout their areas tothecylindrical configuration of the duct walls when retracted, meanspivoting the downstream edges of said guard sections to said duct wallnear a diameter thereof, the downstream edge of each guard portioninterfitting closely with a portion of the wall of the duct to preventthe passage of debris therebetween when the guard is extended, a pocketin the duct wall in the area covered by each guard section whenretracted to accommodate the debris which accumulated on the sectionwhen extended, and means out of the path of the fluid at all times toactuate the guard sections from retracted position to extended matingposition and vice versa.

2. An air intake duct and retractable guard system,

said duct having a wall'of full circular form for feeding "s the ductwith the guard leading edges other and the trailing edges substantiallyengaging said wall to prevent the passage (:5 particles therebetween,and an inoperative position in which the portions are substantially outof the path of fluid flowing through the duct, the cylindrical shapedportions having substantially the same radius as the duct so as toconform throughout with the wall thereof against which they areretracted, and operating means wholly out of the path of fluid flowingthrough the duct being connected to move the guard portions between thesaid two positions.

3. A duct and guard system as claimed in claim 2 which the guardportions are in the form of grids composed of a number of bars in theform of strips which are fiat at least transversely and are arranged intwo sets, those of one set being straight and lying in planes engagingwith each parallel to axis of the intakeduet and extending substantiallylengthwise of the duct when the guard portion is in its inoperativepositio 1, and those of the other set being'curve'd and lying inparallel planes which are at right-angles to the above-mentioned planesand are parallel to the axis of the duct when the guard grid is in itsoperative position.

References Cited in the file of this patent

